Читать книгу Walking in the Yorkshire Dales: South and West. Wharfedale, Littondale, Malhamdale, Dentdale and Ribblesdale онлайн

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The character of the Howgills clearly sets them apart from the rest of the Dales and, with the Middleton Fells, they are separated from the Askrigg Block by another fracture line – the Dent Fault. This runs in a rough north–south line east of Sedbergh, but here the displacement has been in the opposite direction, elevating the older rocks that lie to the west. Geologically these hills are part of the Lake District and are composed of much-folded metamorphosed slates and grits from the Silurian period, about a hundred million years older than the Carboniferous rocks making up the Askrigg Block. Their grassy flanks sweep steeply upwards from deep ravines to broad rounded tops, whose long interconnecting ridges, once attained, offer immensely satisfying walking.

Some of the most spectacular scenery of the park is to be found in the areas dominated by the Great Scar Limestone – Malham Cove, Gordale, Kingsdale, Twisleton, Lower Ribblesdale and the middle reaches of Wharfedale. Towering lines of white cliffs and scars, shake holes, sinks, potholes, caves, disappearing and resurgent streams and rivers, dry valleys and waterfalls, clints and grikes are all features of this remarkable karst landscape. Overlooking the fault lines, the cliffs result from the upward movement of the Askrigg Block, but the terraces along the valley side are due to the relative resistance of different layers to erosive weathering. A similar picture is seen in the Yoredale Series, where the successive bands of limestone are comparatively harder than the intervening strata of sandstones, producing a stepped profile such as that vividly presented above Buckden. It is this same process that gives rise to the many spectacular waterfalls of the region, the water cascading over a lip of hard limestone, but undercutting into the softer rock which lies below.